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<div class="section" id="using-your-own-custom-data-types">
<h1>Using your own custom data types<a class="headerlink" href="#using-your-own-custom-data-types" title="Permalink to this headline">ΒΆ</a></h1>
<p>You can make your own data types by subclassing Table (or other PyTables types,
such as <a class="reference internal" href="../usersguide/libref/hierarchy_classes.html#tables.Leaf" title="tables.Leaf"><tt class="xref py py-class docutils literal"><span class="pre">tables.Leaf</span></tt></a>).
This can be useful for storing a specialized type of data or presenting a
customized API.</p>
<p>Here’s one way to do it, taken from
<a class="reference external" href="http://sourceforge.net/mailarchive/message.php?msg_id=200805250042.50653.pgmdevlist%40gmail.com">http://sourceforge.net/mailarchive/message.php?msg_id=200805250042.50653.pgmdevlist%40gmail.com</a></p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">numpy</span> <span class="kn">as</span> <span class="nn">np</span>
<span class="kn">import</span> <span class="nn">numpy.ma</span> <span class="kn">as</span> <span class="nn">ma</span>
<span class="kn">import</span> <span class="nn">tables</span>
<span class="kn">from</span> <span class="nn">tables</span> <span class="kn">import</span> <span class="n">File</span><span class="p">,</span> <span class="n">Table</span>
<span class="kn">from</span> <span class="nn">tables.file</span> <span class="kn">import</span> <span class="n">_checkfilters</span>
<span class="kn">from</span> <span class="nn">tables.parameters</span> <span class="kn">import</span> <span class="n">EXPECTED_ROWS_TABLE</span>
<span class="k">class</span> <span class="nc">MaskedTable</span><span class="p">(</span><span class="n">Table</span><span class="p">):</span>
<span class="n">_c_classId</span> <span class="o">=</span> <span class="s">'MaskedTable'</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">parentNode</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span>
<span class="n">title</span><span class="o">=</span><span class="s">""</span><span class="p">,</span> <span class="n">filters</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span>
<span class="n">expectedrows</span><span class="o">=</span><span class="n">EXPECTED_ROWS_TABLE</span><span class="p">,</span>
<span class="n">chunkshape</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">_log</span><span class="o">=</span><span class="bp">True</span><span class="p">):</span>
<span class="n">new</span> <span class="o">=</span> <span class="n">description</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">new</span><span class="p">:</span>
<span class="n">maskedarray</span> <span class="o">=</span> <span class="n">description</span>
<span class="n">description</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="nb">zip</span><span class="p">(</span><span class="n">maskedarray</span><span class="o">.</span><span class="n">filled</span><span class="p">()</span><span class="o">.</span><span class="n">flat</span><span class="p">,</span>
<span class="n">ma</span><span class="o">.</span><span class="n">getmaskarray</span><span class="p">(</span><span class="n">maskedarray</span><span class="p">)</span><span class="o">.</span><span class="n">flat</span><span class="p">),</span>
<span class="n">dtype</span><span class="o">=</span><span class="p">[(</span><span class="s">'_data'</span><span class="p">,</span><span class="n">maskedarray</span><span class="o">.</span><span class="n">dtype</span><span class="p">),</span>
<span class="p">(</span><span class="s">'_mask'</span><span class="p">,</span><span class="nb">bool</span><span class="p">)])</span>
<span class="n">Table</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">parentNode</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span>
<span class="n">description</span><span class="o">=</span><span class="n">description</span><span class="p">,</span> <span class="n">title</span><span class="o">=</span><span class="n">title</span><span class="p">,</span>
<span class="n">filters</span><span class="o">=</span><span class="n">filters</span><span class="p">,</span>
<span class="n">expectedrows</span><span class="o">=</span><span class="n">expectedrows</span><span class="p">,</span>
<span class="n">chunkshape</span><span class="o">=</span><span class="n">chunkshape</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="n">byteorder</span><span class="p">,</span>
<span class="n">_log</span><span class="o">=</span><span class="n">_log</span><span class="p">)</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">new</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">attrs</span><span class="o">.</span><span class="n">shape</span> <span class="o">=</span> <span class="n">maskedarray</span><span class="o">.</span><span class="n">shape</span>
<span class="k">def</span> <span class="nf">read</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">start</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">stop</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">step</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">field</span><span class="o">=</span><span class="bp">None</span><span class="p">):</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">Table</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">start</span><span class="o">=</span><span class="n">start</span><span class="p">,</span> <span class="n">stop</span><span class="o">=</span><span class="n">stop</span><span class="p">,</span> <span class="n">step</span><span class="o">=</span><span class="n">step</span><span class="p">,</span>
<span class="n">field</span><span class="o">=</span><span class="n">field</span><span class="p">)</span>
<span class="n">newshape</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">attrs</span><span class="o">.</span><span class="n">shape</span>
<span class="k">return</span> <span class="n">ma</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="n">data</span><span class="p">[</span><span class="s">'_data'</span><span class="p">],</span>
<span class="n">mask</span><span class="o">=</span><span class="n">data</span><span class="p">[</span><span class="s">'_mask'</span><span class="p">])</span><span class="o">.</span><span class="n">reshape</span><span class="p">(</span><span class="n">newshape</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">createMaskedTable</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">where</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">maskedarray</span><span class="p">,</span> <span class="n">title</span><span class="o">=</span><span class="s">""</span><span class="p">,</span>
<span class="n">filters</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">expectedrows</span><span class="o">=</span><span class="mi">10000</span><span class="p">,</span>
<span class="n">chunkshape</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span>
<span class="n">createparents</span><span class="o">=</span><span class="bp">False</span><span class="p">):</span>
<span class="n">parentNode</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">_getOrCreatePath</span><span class="p">(</span><span class="n">where</span><span class="p">,</span> <span class="n">createparents</span><span class="p">)</span>
<span class="n">_checkfilters</span><span class="p">(</span><span class="n">filters</span><span class="p">)</span>
<span class="k">return</span> <span class="n">MaskedTable</span><span class="p">(</span><span class="n">parentNode</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">maskedarray</span><span class="p">,</span>
<span class="n">title</span><span class="o">=</span><span class="n">title</span><span class="p">,</span> <span class="n">filters</span><span class="o">=</span><span class="n">filters</span><span class="p">,</span>
<span class="n">expectedrows</span><span class="o">=</span><span class="n">expectedrows</span><span class="p">,</span>
<span class="n">chunkshape</span><span class="o">=</span><span class="n">chunkshape</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="n">byteorder</span><span class="p">)</span>
<span class="n">File</span><span class="o">.</span><span class="n">createMaskedTable</span> <span class="o">=</span> <span class="n">createMaskedTable</span>
<span class="k">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s">'__main__'</span><span class="p">:</span>
<span class="n">x</span> <span class="o">=</span> <span class="n">ma</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="n">np</span><span class="o">.</span><span class="n">random</span><span class="o">.</span><span class="n">rand</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span><span class="n">mask</span><span class="o">=</span><span class="p">(</span><span class="n">np</span><span class="o">.</span><span class="n">random</span><span class="o">.</span><span class="n">rand</span><span class="p">(</span><span class="mi">100</span><span class="p">)</span> <span class="o">></span> <span class="mf">0.7</span><span class="p">))</span>
<span class="n">h5file</span> <span class="o">=</span> <span class="n">tables</span><span class="o">.</span><span class="n">openFile</span><span class="p">(</span><span class="s">'tester.hdf5'</span><span class="p">,</span><span class="s">'w'</span><span class="p">)</span>
<span class="n">mtab</span> <span class="o">=</span> <span class="n">h5file</span><span class="o">.</span><span class="n">createMaskedTable</span><span class="p">(</span><span class="s">'/'</span><span class="p">,</span><span class="s">'random'</span><span class="p">,</span><span class="n">x</span><span class="p">)</span>
<span class="n">h5file</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
<span class="k">print</span> <span class="nb">type</span><span class="p">(</span><span class="n">mtab</span><span class="p">)</span>
<span class="k">print</span> <span class="n">mtab</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
<span class="n">h5file</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="n">h5file</span> <span class="o">=</span> <span class="n">tables</span><span class="o">.</span><span class="n">openFile</span><span class="p">(</span><span class="s">'tester.hdf5'</span><span class="p">,</span><span class="s">'r'</span><span class="p">)</span>
<span class="n">mtab</span> <span class="o">=</span> <span class="n">h5file</span><span class="o">.</span><span class="n">root</span><span class="o">.</span><span class="n">random</span>
<span class="k">print</span> <span class="nb">type</span><span class="p">(</span><span class="n">mtab</span><span class="p">)</span>
<span class="k">print</span> <span class="n">mtab</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
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